Many consumer product packages known in the art utilize manually-actuated pump sprayers to effectively atomize and evenly disperse products. U.S. Pat. No. 4,958,754, issued Sep. 25, 1990 to Dennis discloses such a package for use with products such as window cleaners, hair sprays, insect poisons, carpet cleaners, automotive cleaners, and the like. Although such pump sprayers are very effective at distributing a bulk liquid over a large coverage pattern area, some applications are unsuitable for spray delivery. For example, when a product is applied in a confined area such as a shower stall, fine spray droplets may be inadvertently inhaled by the user creating potential health problems including damage to the respiratory system.
The pump sprayer industry has responded to these health concerns by designing foaming nozzles that effectively aerate spray droplets to form a foamed spray having a minimal number of unwanted fine spray particles. These foamed sprays comprise large foamed particles having a plurality of bubbles which not only reduce health risks, but, have performance benefits. The performance benefits include improved visibility of the foamed product on the surface to be cleaned, visually signaling the consumer the area is adequately covered by the product. Furthermore, in context of cleaning products, the presence of foam provides the consumer with a perception that cleaning is taking place. Finally, foamed sprays provide improved cling to vertical surfaces avoiding product run off as is experienced with most liquid sprays.
Despite the advantages foamed sprays have over liquid sprays, consumers continue to demand improvements for foamed sprays. For example, consumers prefer that foamed sprays have a wide and uniform coverage pattern to minimize the number of pump strokes required to cover a targeted surface. Consumers also prefer that the foamed sprays exhibit better cling to the vertical surfaces they are applied to, thereby facilitating neater and more efficient use of the product. In context of a cleaning product, good cling to a non-horizontal surface increases the products residence time on the dirty surface to facilitate the breakdown of dirt and grime and its subsequent removal from the surface.
Consumers also desire foam dispensing systems requiring only minimal force and work to dispense. Foam dispensing systems are not preferred by consumers if they require significant effort to actuate, or where multiple strokes are required to cover large surfaces. This effort becomes especially difficult and cumbersome for those having arthritic finger and hand joints. Generally, foam dispensing systems should not require the fluid to travel through tortuous paths resulting in significant consumer effort to dispense the product. Finally, it is desirable that foamed sprays be delivered without experiencing undue messiness. Many foam dispensing systems known in the art do not provide sufficient momentum to the foamed particles so that they reach the targeted surface. This results in foamed sprays depositing on non-targeted surfaces as well dripping on the consumer.
The prior art discloses devices designed for the production of foamed sprays. Such devices apply techniques for mixing air with liquid spray droplets to create a foamed spray. For example, there is a large body of patent literature related to highly mechanized and automated devices for the production of large volumes of foam for fire extinguishing purposes. The foam utilized in this prior art, however, consists of discrete bubbles in a continuous air phase and is commonly characterized by the term "fog" foam. U.S. Pat. No. 2,645,292, issued Jul. 14, 1953 to William's, discloses fog foams produced by passing the fire extinguishing fluid through a screen in order to create a cloud of bubbles. However, such a cloud or fog foam disclosed therein is unsuitable for most consumer products for the reasons mentioned above regarding health problems and usage efficiency.
The art discloses foam dispensing systems better suited for consumer products than mentioned above. Such systems include manually-actuated pump sprayer as disclosed in U.S. Pat. No. 3,946,947, issued Mar. 30, 1976 to Schneider. In one embodiment disclosed by Schneider, the foaming nozzle features a restriction in the form of a venturi located downstream of the spray discharge orifice of a pump sprayer. Said venturi reduces the air pressure surrounding the spray droplets and allows ambient air to be sucked into the venturi via a plurality of air passages in the foaming nozzle of the sprayer located upstream of the venturi. The inclusion of air causes aeration of the liquid spray droplets just before they impinge on the convergent portion of said venturi resulting in turbulence of the liquid and air mixture, therein forming a foamed spray. The venturi has an optimum length to control the degree of mixing of the air and liquid in order to form highly mixed foamed sprays.
Although the foamed spray produced by the above-mentioned system generally has good quality, the spray angle of the discharged foam is substantially interrupted by the above-mentioned restriction in the foaming nozzle. This results in the foamed spray having a narrow spray pattern which requires multiple pump strokes to adequately cover a surface. In addition, the narrow pattern concentrates the foam over a smaller area thereby encouraging product run-off. Furthermore, the disclosed system has a long foaming nozzle, requiring added work to pump the sprayer to overcome the resistance to the flow of product through the foaming nozzle. Said foaming nozzle is also responsible for engineering complexity and added material cost as compared to typical nozzles.
More recently, other improved means for producing turbulence by impingement of the liquid spray have been developed. These means include forcing the liquid spray to impinge on the inner surface of a cylindrically shaped wall of a foaming nozzle. Exemplary dispensing systems featuring such designs, as well as additional features such as on/off positions or liquid spray/foamed spray positions to foaming nozzles are disclosed in U.S. Pat. No. 4,767,060, issued Aug. 30, 1988 to Shay et al.; U.S. Pat. No. 4,779,803, issued Oct. 25, 1988 to Corsette; and U.S. Pat. No. 5,158,233, issued Oct. 27, 1992 to Foster et al. Although these systems have overcome the disadvantageous engineering complexity and material cost as previously mentioned, the spray angle is still sufficiently interrupted, producing narrow foamed spray patterns and the problems associated with such patterns as mentioned above.
Other systems disclosed in the art utilize spray impinging obstacle walls positioned directly in the path of the liquid spray to produce a foamed spray. U.S. Pat. No. 4,350,298, issued on Sep. 21, 1982 to Tada discloses a pump sprayer including a foaming nozzle having an outlet wall extending across the entire cross sectional area of the nozzle. This wall is comprised of a plurality of arms radially extending from the center of the wall. Liquid spray droplets collide with the arms in the presence of ambient air in the foaming nozzle to create a foamed spray. Said foamed spray exits the foaming nozzle through openings between the radial arms of the outlet wall.
In another example, U.S. Pat. No. 4,925,106, issued May 15, 1990 to Maas et al. discloses a perforated wall placed downstream of the spray discharge orifice, whereby a divergent spray impinges with said wall and is randomly deflected, mixing with air in the foam chamber to create a foam. Other similar foam forming obstruction devices are disclosed in U.S. Pat. No. 4,646,973, issued Mar. 3, 1987 to Focaracci and U.S. Pat. No. 4,730,775, issued Mar. 15, 1988 to Maas. Although such systems successfully transform spray droplets into foamed sprays, the resultant coverage pattern is inadequate for many applications, since the spray is being substantially interrupted and redirected.
Foaming nozzles for pump sprayers disclosed in the prior art also utilize screens to transform liquid spray droplets into a foamed spray. U.S. Pat. No. 4,603,812, issued Aug. 5, 1986 to Stoesser et al., discloses a foam dispensing system comprising a screen having a size from about 60 to 200 mesh U.S. Sieve Series, located downstream of a spray discharge orifice, and a means for introducing air into the foaming nozzle. Stoesser' nozzle, having the mesh sizes disclosed therein, produces foamed sprays of high quality with superior cling to a vertical surface, and with a spray pattern that is substantially the same as the spray pattern of droplets absent the foaming nozzle. However, Stoesser's fine mesh screen is susceptible to clogging. Stoesser also discloses that "screens having a smaller mesh size than that indicated will severely reduce spray velocity and cause excessive dribbling, whereas screens having a larger mesh size will permit spray to pass therethrough without sufficient foaming."
Accordingly, it is an object of the present invention to provide a foam dispensing system for a foamable liquid which produces a high quality foamed spray with superior cling to vertical surfaces, and with a spray pattern that is substantially the same as the spray pattern of droplets absent the foaming nozzle, and also which minimizes nozzle screen clogging.
It is also an object of the present invention to provide a foam dispensing system having a less expensive screen to mold or to weave by virtue of using a coarser screen than those having mesh sizes above 60.